Photographic timing apparatus

ABSTRACT

A device is disclosed for accumulating, for three primary colors, the log times required to print photographically a population of negatives, and to count the negatives in the population. Based on such accumulations, the average log times of the population may be determined; and from such average log times, a setup calibration patch may be formulated for the printer. The device embodies an improved log time pulse generator.

United States Patent [72] Inventors Filed Patented Assignee Appl. No.

Terry E. Riley;

Raymond G. Rogers, both of Rochester,

June 17, 1970 Oct. 12, 1971 Eastman Kodak Company Rochester, N .Y.

8 Claims, 7 Drawing Figs.

PH 0 TOG RA PH/C COL 0F? FRI/V TE)? STARTS I PHOTOGRAPHIC TIMINGAPPARATUS US. Cl

Int. Cl G03b 27/76 Field of Search 355/38, 35;

Lag

[56] References Cited UNITED STATES PATENTS 3,120,782 2/1964 Goddard etal.. 355/38 X 3,519,347 7/1970 Bowker et al.... 355/38 X 3,527,5409/1970 Bowker et al 355/38 X Primary Examiner-Samuel S. MatthewsAssistant Examiner-Richard A. Wintercom Attorneys- Walter O. l-lodsdonand Robert F. Cody fir e g Q /a GREEN DENSITY 0F POPULATION Total log ZN AVE/i 8L UE DE NSI T Y 0F POPUL A 7/0 PAIENTEuucI 12ml 3,612,683 SHEET30F 4 START CONTROL EXPOSURE RING FROM COMPARATUR ourpur FIG. 5 g 640 ab c d e f L06 r O T0 |+O EXPOSURE COUNTER TERRY ET RILEY RAYMOND 6.ROGERS INVENTORS Maw QM 2 A TTORNE Y5 PHOTOGRAPHIC TIMING APPARATUSBACKGROUNB OF THE INVENTION 1. Field of the Invention This inventionrelates in general to photographic timing apparatus, and in particularto apparatus for determining the logarithms of various time measures,and of various time dependent variables.

The invention provides a device which is useful for producing a measureof the average time that it takes (for each of three color domains) toprint photographically a population of film negatives.

2. Description Relative to the Prior Art A typical photographic printerfor making color prints from color negatives has a white light sourcetherein, and positionable cyan, magenta, and yellow filters forselectively blocking the red, green, and blue components of the whitelight source from reaching the paper being photographically printed.During printing, the color filters are positioned to intercept thesource light, after respective response durations which are inproportion to the respective color densities of the negative beingprinted. it has been the practice heretofore to include in such aprinter an additional compound filter which has transmission densities,for red, green, and blue, which are such that, when printing from anaverage" negative, all positionable filters pull-in together tointercept the source light. Thus, not only will efficient operation ofthe printer obtain, but also the printer will produce better qualityprints, Le. a color sensitive layer within the print material will notbe exposed, via other color channels, after its own respective filterhas been pulled-in.

To provide the above-mentioned simultaneous filter pull-in for anaverage negative, it is customary in the art to calibrate a printer byuse of a setup patch." A setup patch is a negative having colordensities like the densities of an average negative which is to behandled by the printer. Thus, a compound filter is selected so that whenprinting the patch, all positionable filters pull-in together.

Since the kinds of prints that photofinishers make will vary from seasonto season, from photofinisher to photofinisher, from photographer tophotographer, etc., the characteristics of the setup patch should vary;and therefore, depending on printing conditions, the setup calibration(and the patch) must be checked periodically.

The color densities of negatives processed by a printer are manifestedin the logarithms of the exposure durations T which are commanded by thedensitometry apparatus of such printer (i.e., d-log E-log T). It hasbeen the practice heretofore for a phototechnician to accumulate (foreach of three primary colors) the respective times required to print agiven population of film negatives; then to take the logarithm of eachof such time, then to add such log times, and then to divide such logtime total by the number of negatives in the population to determine theaverage log time (average density) required to print the negatives inthe population. Bases on such average log time, for each of the threeprimary colors, setup patches were then prepared.

SUMMARY or THE INVENTION Apparatus embodying the invention is adapted tobe plugged into a photographic printer; and in response to the operationof the printer produces both an indication of the number (N) of exposureproduced by the printer, and an indication of the total of thelogarithms of the times (log T) required to make such exposures.Division of the total log T by N may either be automatic, or it may becalculated, thereby to determine the average log time required to printthe N negatives.

Essential to the effectiveness of apparatus according to the inventionis a specially designed pulse generator for producing, for each negativeprocessed through the printer, pulses at logarithmically spaced times,the total number of such produced pulses being representative of thelogarithm of the actual time that occurs between the first and the lastof the pulses. Thus, in a simple version of the invention, if theexposure duration of a printer goes from l00 milliseconds, then to 200milliseconds, then to 400 milliseconds, and then finally to 800milliseconds, four pulses will be produced, indicating a log time countof four for the exposure. By multiplying such count by a constant (inthis case, 0.301) that equals the difference in the logarithms (base 10)of any pair of adjacent pulse-producing times, the log time of theexposure may be determined.

To produce pulses at logarithmically spaced times, apparatus accordingto the invention employs a clock pulse generator, a counter responsiveto count the clock pulses, and a count memory, cooperative with thecounter, for triggering the production of log time count pulses when thememory count and the counter count coincide.

The design of the memory is of special importance, and consideration:

As implied above, the logarithm (to any base, say 10) of a time variable(i.e. log T) increases linearly when the time variable incremeslogarithmically (even to a different base, say 2); and therefore ameasure of the log of the time variable may be determined by countingpulses which are forced to occur at the logarithmically increasingtimes. By stating the logarithmically increasing time variable in binaryform, each value thereofwill be like each other value, save for amultiplier factor of 2 (i.e. a binary shift). Thus,

TABLE I Logarithmicllly Binary Notation (Base 2) Arranged of theLogarithmi- Tirne T in Decimal Log T cally Arranged Notation Time 1 I002 0| l00l00 :Alog T=0.30l0 200 2,3010: 0ll00l000 :Alog T=0.30l0 4002.6021: 0ll00l0000 :Alog T=0.30l0 800 2.90M: 0ll00l00000 :Alog T=0.30l0L600 3.204]: 0ll00l000000 Corollarily, if the logarithmically increasing(base 2) decimal times are arranged in sets, the binary notations forsuch sets will also be in sets, and the corresponding terms of each suchset will be alike, save for multiplier factors of 2 (Le. binary shifts).Thus,

A memory in accordance with table II above is employed by apparatusaccording to the invention; and therefore such memory need store onlysix discrete counts (provided, of course, that shifting is implemented).INn a presently preferred form of the invention, as will be appreciatedlater, such shifting, rather than being direct, is simulated in a waythat minimizes the number of stages which are required for theabove-mentioned counter.

OBJECTS OF THE INVENTION To provide a device that will accumulate thelog times that are required to print photographically film negatives;and further to provide, for use in such a device, an improved pulsegenerator for producing a chain of pulses having a logarithmicoccurrence rate.

The invention will be described with reference to the FIGURES, wherein:

FIG. 1 is a basic block diagram illustrating the cooperation between aprinter and the device of the invention,

FIG. 2 is a block diagram indicating a pulse generator according to theinvention,

FIG. 3 is a block diagram indicating a presently preferred variation ofthe pulse generator indicated in FIG. 2,

FIG. 4 is a block diagram depicting the arrangement and interconnectionof circuits employed in the device of the invention,

FIG. 5 is a diode memory matrix useful for implementing the invention,

FIG. 6 indicates a pulse generator circuit useful for simulating theshifting of memory counts, and

FIG. 7 is a diagram of a circuit useful for preventing unusually exposednegatives from influencing the negative count accumulation which isregistered by the device of the invention.

Referring to FIG. 1, a photographic printer 10 is indicated processingphotographic negatives and producing therefrom photographic prints. Theprinter 10 forms no part of the invention, but produces signals N and Twhich are monitored by the log time totalizer apparatus 12 according tothe invention. The subscripts R,G,B stand for red, green, and blue. Thesignal N, which occurs at the start of each exposure performed by theprinter 10, is applied to an accumulator 14 so that a count may be madeof the number of negatives processed by the printer 10. The signals T,which will vary from negative to negative, represent the respectivedurations that the densitometer section of the printer l0 commands forthe color exposures which are to be for printing the respectivenegatives.

The log time totalizer 12 includes therein devices 16 for producingsignals representing the logarithms of the duration signals T andaccumulators 18 for totaling the log times so produced. Divider devices20 responsive to the totaled log time and negative count signals,produce quotient signals representing the average log times required toprint, in each of the three primary colors, from the population ofnegatives processed by the printer [0; and based on such average logtimes, a setup patch may be made so that efficient and effective use ofthe printer will obtain. The divider devices 20, are depicted in phantomto indicate that, if preferred, the divisions need not be performedautomatically.

As noted above, the invention proposes the generation of a number ofpulses, representing the logarithm of time, by effectively countingclock pulses until a stored count, in binary form, has been reached; andthen, in response to such happening, doing two things: (a) producing alog time count pulse, and (b) shifting the stored count in order toproduce a new higher order count for comparison with the clock pulsecount. With the above as background, consideration should be given toFIG. 2: A clock pulse generator 22 is adapted, say during the time thata red exposure is to be made, into a printer, to

have its pulses counted by a counter 24. Stored in a shiftable memory 26is a reference count; and both the counter 24 count and the memory 26count are applied to a digital comparator 28, which may be of anywell-known type. When the counter 24 count reaches the memory 26 count,the comparator 28 produces an output pulse, which gets applied both toan accumulator (not shown) and to the memory 26 to shift the storedcount. The above is then repeated, only now the count of the counter 24is compared with the shifted count, etc.; and as a result, the output ofthe comparator 28 is a pulse train that has a logarithmic occurrencerate, which is to say that an accumulator responsive to the pulse trainwould record a count equal to the logarithm of the duration during whichclock pulses are applied to the counter 24.

Whereas the circuit of FIG. 2 is effective for its intended purpose solong as the counter 24 has enough stages to count to the repeatedlyshifting memory 26 count, a modification of the circuit of FIG. 2, byelTectively simulating count shifting, permits the use of a counterhaving a minimal number of stages:

Referring to FIG. 3, a clock pulse generator 22' applies pulses to acounter 24 during the time that a red exposure is being made in aprinter, A memory device 26' stores a reference count; and a digitalcomparator 28' compares the count of the counter 24' with the memory 26'count, producing at coincidence a log time pulse. Rather than apply thelog time pulse to shift the memory count, such pulse is employed (a) tohalve the rate at which clock pulses are applied to the counter 24' and(b) to halve the count of the counter 24. That this has the efi'ect ofshifting the memory count, as in connection with the apparatus of FIG.2, may be seen from the following: Assuming the memory 26' stores abinary count representing decimal I00, and that clock pulses occurinitially at l millisecond intervals. At 100 milliseconds after astart," the comparator 28 produces a log time pulse, and simultaneouslyhalves the clock pulse rate, and the counter 24 count (i.e. the shiftsthe counter count one place to the right so that the counter 24' hastherein the binary equivalent of decimal With clock pulses now occurringevery 2 milliseconds, 50 clock pulses occur during the next 100milliseconds; but since the counter 24' starts counting with a biascount of 50," a second log time pulse occurs at 200 milliseconds afterthe start. The second log time pulse again halves the clock pulse rate,and the count of the counter 24. Since clock pulses now occur every 4milliseconds, 50 clock pulses occur during the time between 200milliseconds and 400 milliseconds after the start; and since the counter24 again starts counting (at 200 milliseconds) with a bias count of 50,"a third log time pulse occurs at 400 milliseconds after the start," etc.Thus, it is seen that at 100 milliseconds, 200 milliseconds, 400milliseconds, etc., pulses are forced to occur.

Apparatus according to the invention, in its presently preferred fonn,relies on the principles associated with the apparatus of FIG. 3, asmodified in accordance with the concepts implicit in table II above.

Referring then to FIG. 4, a variable frequency pulse rate generator 30is adapted to produce clock pulses at a first frequency F,, then at asecond frequency F, which is half the frequency F then at a thirdfrequency which is half the frequency I}, etc. To this end, a shiftregister 32 is adapted to arm successive pulse sources 34,, 34,, etc.;and such pulse sources 34 apply their respective outputs, via an ORcircuit 36, to a binary counter 38. At the start of an exposure, withina printer with which the device of FIG. 4 is cooperative, the counter 38is cleared and a SET signal is applied to the register 32 so that,initially, pulses at the highest pulse rate (F,) are applied to thecounter 38. Simultaneous with the start of the F pulses, a ring counter40 is set so that the first of a set of memorized eight-bit counts mayberead out of a memory 42 and applied to a count comparator 44. The memory42 stores six counts (see table II) which are so logarithmically (base10) related that the difierences between the logarithms (base l0)thereof will be substantially linearly disposed. The comparator 44includes an array of eight exclusive NOR circuits 46 (a-h) which receivethe corresponding bits of the counter (38) and memory counts and, whensuch counts are identical, an-AND circuit 48 produces an output pulse,i.e. a log time pulse.

The log time pulse from the AND circuit 48 is applied to AND circuits50, 52, 54; which circuits also receive gating signals, respectively,for as long as the red, green, and blue exposures are being made in theprinter with which the FIG. 4 device is cooperative.

The pulse output from the AND circuit 48 is also applied to step thering counter 40 so that, as each log time pulse occurs, the ring countercauses the memory 42 to present a new eightbit count for purposes ofcomparison with the count of a counter 38. Since the set of memorycounts are logarithmically disposed (base the occurrence rate of pulsesat the output of the AND circuit 48 is logarithmic (base 10). When thelast of the memory counts has resulted in a log time pulse, however, thering count 40-while switching back to the first of the memorycircuits-causes a pulse to be applied to an AND circuit 56. The ANDcircuit 56 also receives the log time pulses and, thus, after eachfull'run through the counts of the memory 42, a pulse is applied fromthe AND circuit 56 (a) to step the register to a halved" pulsefrequency, and (b) to halve the count of the counter 38 by a shiftright." Such a practice is in accordance with the teaching of FIG. 3,and table II, and reeultsby virtue of "base 2 shifting-in a train ofpulses which are, timewise, logarithmically disposed (base 10); and suchpulse train occurs without the need to memorize a large number ofreference counts, and without the need for a counter with a large numberof stages.

Subject to a limitation to be discussed presently, each negative whichis processed through a printer, with which the device of FIG. 4 iscooperative, causes a pulse to be applied to a counter 58. Thus, knowingthe number of negatives and the total log time counts for the red,green, and blue exposures for all the negatives which have beenprocessed through a printer, the average log times for suchnegatives-for red, green, and blue-may be obtained; and from suchaverage log times the above-mentioned setup patch may be produced.

To prevent negatives which are unusually underexposed (say thoserequiring an exposure time which is less than 100 milliseconds) frominfluencing the averaging of log times, apparatus according to theinvention includes therein a network 60 which assures that suchunderexposed negatives do not get counted in making averages. Theoperation of this network will be discussed later in connection withFIG. 7.

Referring to FIG. 5, the cooperation of the ring counter 40 and thecount memory 42 will now be discussed: When the ring counter 40 excitesrespectively, and successively, lines a through f of the memory 42,memory diodes 62 within the memory get biased to produce, on the memoryoutput contacts 64 a-h, the time counts 01100100; 01110000; 01111110;10001101; 10011110; 10110010. And, it is the bits of these time countswhich are compared with the bits of the counter 38 counts (by means ofthe exclusive NOR circuits 46 a-h) to produce log time pulses.

Referring to FIG. 6, the variable pulse rate generator 30 will now bediscussed: A clock pulse generator 66 produces pulses, say, at the rateof one pulse per millisecond. The clock pulse generator 66 applies toits pulses to an AND circuit 681, and to the first of a series ofinterconnected divide-by-two circuits 70. Each divide-by-two circuitincludes a pair of AND circuits 74, 76 which cooperate to set and reseta flip-flop 78. With the flip-flop circuit 78 initially in its ONEstate, the first clock pulse passes through the circuit 74, and throughan AND circuit 80. The first clock pulse, in passing through the ANDcircuit 74, causes the flip-flop 78 to switch to its ZERO state. Withthe flip-flop 78 now in its ZERO state, the second clock pulse passesthrough the AND circuit 76 to switch the flip-flop back to its ONEstate; but since the clock input to the AND circuit 76 is isolated fromthe AND circuit 80, such second clock pulse is prevented from passingthrough the AND circuit 80. The above is repeated for the third andfourth pulses, the fifth and sixth pulses, etc., so that the AND circuitproduces a stream of pulses which occur at one-half the rate at whichthe clock pulses occur. In like manner, other divide-by-two circuits 70halve the frequencies of their respective input pulse trains. Eachdivide-by-two circuit 70 cooperates with a respective AND circuit 68through 68 and the AND circuits 681 through 68W are successively armedby the shift register 32.

Concerning the minimum time network 60, which assures against countingunusually short exposures in the average process, reference should behad to FIG. 7: The initiation of the exposure period causes a flip-flopto switch to its ONE state (if it is not already in such state); andsuch exposure initiation arms an AND circuit 92 which is disposed topass pulse signals which occur when the flip-flop 90 switches from itsONE state to its ZERO state. As soon as the first log time pulse exitsfrom the AND circuit 48 (FIG. 4)indicating a log time count which is atleast long enough to be counted in the averaging process, the flip-flop90 switches back to its ZERO state. This action causes the exposurecounter 58 to register a count; and subsequent log time pulses for thenegative being printed have no effect on the counter 58 since theflipflop 90 has already been set to its ZERO state.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

What is claimed is: v

1. Log time accumulator apparatus for use with a color photographicprinter of the type having means for producing signals for signallingthe start of an exposure within said printer and the duration of thered, green, and blue portions of said exposure comprising:

a. first means responsive to said exposure start signals fo counting thenumber of such signals produced by said printer while processing a givenpopulation of photographic negatives,

b. second, third, and fourth means responsive to said signalsrepresenting said red, green, and blue durations respectively, forproducing signals that correspond with the logarithms of said durations,and

. fifth, sixth, and seventh means for accumulating respectively saidlogarithmic signals, and producing therefrom respective countsrepresenting accumulated log times, whereby the respective red, green,and blue average log times for exposures within said printer may bedetermined by dividing the respective accumulated log time counts by thecount of said first means.

2. Log time accumulator apparatus for use with a color photographicprinter of the type having means for producing signals for signallingthe start of an exposure within said printer and the duration of thered, green, and blue portions of said exposure comprising:

a. first means responsive to said exposure start signals for countingthe number of such signals produced by said printer while processing agiven population of photographic negatives,

b. first, second, and third gate means respectively responsive to saidsignals representing said red, green, and blue portions of said exposureduration,

0. first, second, and third accumulating means, cooperative with saidfirst, second, and third gate means, for counting pulses respectivelyapplied to said first, second, and third accumulating means,

d. a source of timed pulses,

e. a memory device for storing signals representing at least onereference count in binary form,

f. a counter for binary counting said timed pulses,

g. means for comparing signals representing the count of said counterwith said signals representing said reference count and producing, whenthe said signal counts are the same, an output pulse, and

h. means responsive to said output pulse for altering at least one ofthe sources of comparison counts so that a longer duration occursbetween subsequent pairs of output pulses than former pairs of outputpulses, said output pulses being applied through said first, second, andthird gate means to respectively said first, second, and thirdaccumulating means.

3. The apparatus of claim 2,

a. wherein said memory device stores signals representing a plurality ofcounts all of which are sufficiently different from each other thattheir respective logarithms, to the base 10, increase in a linearmanner, and

b. wherein said apparatus includes means responsive to said outputpulses to apply successively the signals representing said counts to thesaid means for comparing signals.

4. The apparatus of claim 2,

a. wherein said source of timed pulses is a variable frequency pulsesource,

b. wherein said counter is shiftable,

c. wherein said means responsive to output pulses cyclically appliessuccessively the signal representative counts to said signal comparingmeans, and

d. wherein said means for altering the sources of comparison countscooperates, at the start of each new cyclic application of signal countsto said signal comparing means, with said pulse source and said counterto halve the pulse rate of the source and shift the count of the counterdownwardly one binary bit.

5. The apparatus of claim 3,

a. wherein said source of timed pulses is a variable frequency pulsesource,

b. wherein said counter is shiftable,

c. wherein said means responsive to output pulses to apply is a ringcounter,

d. wherein said apparatus includes means for producing a step signalwhen the ring counter switches from its highest count to its lowestcount, and

e. wherein said means for altering the sources of comparison countscooperates, in response both to said output pulses and to said stepsignal, with said pulse source and said counter to halve the pulse rateof the source and shift the counter downwardly one binary bit.

6. The apparatus of claim 2 including means for preventing said firstmeans from counting until at least one pulse has been applied to any oneof said accumulating means.

7. A log time base pulse generator comprising:

a. a memory of a plurality of binary counts which are sufficientlydifferent from each other that their logarithms, to the base 10, aredifferent from each other by substantially the same amount,

b. a source of timed pulses,

c. a shiftable binary count for counting said timed pulses,

d. count comparison means for receiving the count of said counter,

e. pulse responsive means for applying said memory counts successivelyand cyclically to said count comparison means for comparison with saidcounter counts, said comparison means producing an output pulse when itstwo applied counts are the same, said output pulse being applied to saidpulse responsive means, and

f. means responsive after each cyclic application of memory counts tosaid count comparison means to halve the rate of application of timedpulses to said counter, and to shift downwardly the count of saidcounter by one binary bit.

8. The apparatus of claim 7 wherein said pulse responsive means is aring counter.

1. Log time accumulator apparatus for use with a color photographicprinter of the type having means for producing signals for signallingthe start of an exposure within said printer and the duration of thered, green, and blue portions of said exposure comprising: a. firstmeans responsive to said exposure start signals for counting the numberof such signals produced by said printer while processing a givenpopulation of photographic negatives, b. sEcond, third, and fourth meansresponsive to said signals representing said red, green, and bluedurations respectively, for producing signals that correspond with thelogarithms of said durations, and c. fifth, sixth, and seventh means foraccumulating respectively said logarithmic signals, and producingtherefrom respective counts representing accumulated log times, wherebythe respective red, green, and blue average log times for exposureswithin said printer may be determined by dividing the respectiveaccumulated log time counts by the count of said first means.
 2. Logtime accumulator apparatus for use with a color photographic printer ofthe type having means for producing signals for signalling the start ofan exposure within said printer and the duration of the red, green, andblue portions of said exposure comprising: a. first means responsive tosaid exposure start signals for counting the number of such signalsproduced by said printer while processing a given population ofphotographic negatives, b. first, second, and third gate meansrespectively responsive to said signals representing said red, green,and blue portions of said exposure duration, c. first, second, and thirdaccumulating means, cooperative with said first, second, and third gatemeans, for counting pulses respectively applied to said first, second,and third accumulating means, d. a source of timed pulses, e. a memorydevice for storing signals representing at least one reference count inbinary form, f. a counter for binary counting said timed pulses, g.means for comparing signals representing the count of said counter withsaid signals representing said reference count and producing, when thesaid signal counts are the same, an output pulse, and h. meansresponsive to said output pulse for altering at least one of the sourcesof comparison counts so that a longer duration occurs between subsequentpairs of output pulses than former pairs of output pulses, said outputpulses being applied through said first, second, and third gate means torespectively said first, second, and third accumulating means.
 3. Theapparatus of claim 2, a. wherein said memory device stores signalsrepresenting a plurality of counts all of which are sufficientlydifferent from each other that their respective logarithms, to the base10, increase in a linear manner, and b. wherein said apparatus includesmeans responsive to said output pulses to apply successively the signalsrepresenting said counts to the said means for comparing signals.
 4. Theapparatus of claim 2, a. wherein said source of timed pulses is avariable frequency pulse source, b. wherein said counter is shiftable,c. wherein said means responsive to output pulses cyclically appliessuccessively the signal representative counts to said signal comparingmeans, and d. wherein said means for altering the sources of comparisoncounts cooperates, at the start of each new cyclic application of signalcounts to said signal comparing means, with said pulse source and saidcounter to halve the pulse rate of the source and shift the count of thecounter downwardly one binary bit.
 5. The apparatus of claim 3, a.wherein said source of timed pulses is a variable frequency pulsesource, b. wherein said counter is shiftable, c. wherein said meansresponsive to output pulses to apply is a ring counter, d. wherein saidapparatus includes means for producing a step signal when the ringcounter switches from its highest count to its lowest count, and e.wherein said means for altering the sources of comparison countscooperates, in response both to said output pulses and to said stepsignal, with said pulse source and said counter to halve the pulse rateof the source and shift the counter downwardly one binary bit.
 6. Theapparatus of claim 2 including means for preventing said first meansfrom counting until at least one pulse has been applied to any one Ofsaid accumulating means.
 7. A log time base pulse generator comprising:a. a memory of a plurality of binary counts which are sufficientlydifferent from each other that their logarithms, to the base 10, aredifferent from each other by substantially the same amount, b. a sourceof timed pulses, c. a shiftable binary count for counting said timedpulses, d. count comparison means for receiving the count of saidcounter, e. pulse responsive means for applying said memory countssuccessively and cyclically to said count comparison means forcomparison with said counter counts, said comparison means producing anoutput pulse when its two applied counts are the same, said output pulsebeing applied to said pulse responsive means, and f. means responsiveafter each cyclic application of memory counts to said count comparisonmeans to halve the rate of application of timed pulses to said counter,and to shift downwardly the count of said counter by one binary bit. 8.The apparatus of claim 7 wherein said pulse responsive means is a ringcounter.